Telephone-circuit.



K. S. JOHNSON.

TELEPHONE cmcun.

APPLICATION FILED AUG. 16, 1917.

Patented Feb. 4, 1919.

YORK.

assrenon 'ro WESTERN ELEG- Y., A CORPORATION or new TELEPHONE-CIRCUIT.

ma aise.

Specification of Letters Patent.

Patented Feb. 4%, 11919.

Application filed August 16, 1917. Serial No. 186,485.

To all whom it may concern Be it known that I, KENNETH S. J oHNsoN, a citizen of the United States, residing at Jersey City, in the county of Hudson and State of New Jersey, have invented certain new and useful Improvements in Telephone- Circuits, of which the followmg 1s a full,- clear, concise, and exact descriptlon.

This invention relates to clrcuit arrangements for improving telephonlc transmlssion and is directed more specifically to a circuit arrangement for use at an operators position or at a subscribers station.

It is an object of the invention to improve both the efliciency and the quality of the transmission from the telephone set.

In the ordinary operators telephone set heretofore used, the transmitter is generally included in circuit with the battery, a suitable retardation coil and a primary WlIldlIlg' of an induction coil. A condenser is also usually employed in a bridge connected across the transmitter and the primary of the induction coil or is includedin series with the primary winding of the lnductlon coil.

In such systems, it has been found that while the condenser serves the useful purpose of preventing a flow of current of con-' stant potential through the primary winding of the induction coil and by its continuous charging and discharglng, produces the desired varying current effects n the primary winding, considerable lOSS 1I1 the transmission efiiciency results from its use. It has also. been found that due to the selective nature of the condenser whereby certain frequencies of current are easlly transmitted, while other frequencies are largely suppressed, the quality of the transmission has been somewhat impaired.

In accordance with a feature of this invention, the efiiciency and the quality of the transmission are improved by including in circuit with the primary winding of the induction coil, a source of potential independent of the usual battery which supplles the transmission current, in such a manner that it willoppose a drop in potential resulting from the current which is forced through the transmitter by the usual transmission battery. By virtue of this arrangement, the same effect is obtained as would result from the use of a condenser of infinite capacity.

vder such circumstances,

These and other features not specifically mentioned above will more readily appear from the following specification and the annexed drawing in which a figure shows diagrammatically an operators telephone circuit which embodies the invention.

In the accompanying drawing, the primary portion of the operators circuit is shown as comprising a transmitter 1, an exchange battery 3, and a retardation coil 2, which are connected in the usual manner, and an additional battery 4 included in circuit with primary windings 5, 5 of induction coil 6. The secondary portion of the circuit including the usual receiver 8, and the secondary winding 7 of the induction coil 6, is shown as being connected in the customary manner and is indicated as being adapted for connection, through the agency of alistening key 9 of the usual type, to an ordinary operators cord circuit A of which only a portion is diagrammatically shown.

It is thought that the invention will be more readily understood from a description of its operation. Assuming that the diaphragm of the transmitter 1 occupies a given position, it will be observed that since the additional source of potential is connected so that it will oppose any drop in potential due to current flowing through the transmitter 1, it will be feasible to employ a battery l of such relative proportions that there will be no current flowing through the primary windings 5, 5 of induction coil 6. Un-

the effect upon the transmission of the telephone circuit would be the same as if the were connected across the transmitter 1 and the retardation coil 2, disregarding the remainder of the primary portion of the telephone circuit. Under such conditions the alternating current impedance relations in the primary branch of the operators circuit are the same as would result from the use of a condenser of infinite capacity which would permit the transmission of currents of all frequencies with equal readiness. However, if it is found to be desirable, battery 4 may be chosen as having such potential as will permit a certain definite amount of current to flow through the primary winding of the coil when the diaphragm of the transmitter l occupies the given position.

The vibration of the diaphragm of the transmitter as it is spoken into, causes a exchange battery 3' variation in the resistance of the transmitter. in the usual manner and as a result, a

current of a varying nature flows through the rimary windings 5, 5 of induction co 1l 6. urrent of a corresponding frequency s thereby induced in the ordinary manner in the iecondary winding 7 of the induction coil 6 for transmission through listening key 9 to any subscribers station to which cord circuit A may be connected.

What is claimed is:

1. A station telephone circuit comprising an induction coil, a primary winding therefor, a transmitter and a retardation coil through the primary of said induction coil.

" 3. A station telephone circuit comprising an induction coil, a primary winding therefor, a transmitter, a retardation coil and a source of current connected to said primary winding, and means included with said prima winding for permitting the unrestricted fibw of a periodically varying current of any frequency through said primary Wind- "ing and for opposing the drop in voltage caused by current flowing through said transmitter from said. source of current.

4. A station telephone circuit comprising an induction coil, primary and secondary windings therefor, a transmitter, a retardation coil, and tWo sources of current of different voltages connected to said primary Win ing. said transmitter and said retardation coil for inducing and controlling the flow of current in said secondary winding of said induction coil.

5. A primary circuit for an operators telephone set including a transmitter, a retardation coil, two sources of current of different voltages, and the primary winding of aninduction coil arranged for producing in said primary winding a varying current corresponding in frequency with the vibration of the transmitter diaphragm.

6. In a station telephone circuit, the combination of a source of potential, a trans! mitter, an induction coil, and means opposing the passage of direct current from said source through said induction coil and offering substantially zero impedance to voice currents of any frequency.

7. A telephone circuit comprising an induction coil having a primary winding, a transmitter and a retardation coil connected in circuit with the primary winding, and two sources of current having different voltages included in circuit with the primary winding to provide therein no current flow when the transmitter diaphragm is quiescent and a varying current flow upon the operation of the transmitter.

8. A telephone circuit comprising an induction coil, a primary winding therefor,

a transmitter bridged across the primary winding, a retardation coil and a source of current connected to the primary winding,

and means included with the primary winding for permitting the unrestricted flow of periodically varying currents of any frequency through the primary winding and for opposing the drop in voltage caused by the current flowingthrough the transmitter from the source of current.

In witness whereof, I hereunto subscribe pgyi rname this 14th day of August, A. D.-

KENNETH S. JOHNSON. 

